Interim EPDs
What is an interim?
Interim EPDs are calculated on animals that do not have true EPDs from the weekly American Angus Association National Cattle Evaluations (NCE). An interim value is indicated by an "I" in front of the number. While low in accuracy, an interim value gives you a snapshot of the animal's potential value as a parent, therefore it provides a temporary selection-decision tool until more data is available to calculate a true NCE EPD.
Calculating Interim EPDs
Interim EPDs are calculated using only pedigree information from the animal. As an example, if a bull calf has no performance or genomic data in the weekly evaluation and his parents have true NCE EPDs, then a pedigree-estimated EPD is computed as an average of the parental EPDs.
I-EPD = (0.5 × EPD of sire) + (0.5 × EPD of dam)
The accuracy on the resulting interim is low, at 0.05. With a low accuracy, as data is added to the weekly evaluation for the animal, the true EPD calculated has the potential to change from the interim value. More details about possible change and accuracy can be found here.
How is an NCE EPD different?
The EPDs from the weekly NCE do not have the letter "I" preceding the EPD. These are calculated using all available data for a particular trait, including pedigree, performance, genomic, and progeny data.
The EPDs resulting from NCE have varying accuracies, depending on the amount of information (the animal's own record, progeny records, ancestral records, etc.) that contribute to each animal's predicted genetic value. To be included in the NCE runs, a nonparent animal must have a performance record or genomic result that meets data requirements.
Parent animals have progeny with performance records and are incorporated into the evaluations even if the parent does not have an individual record for the trait of interest. The evaluations to generate EPDs utilize many generations of pedigrees.
Genomic results are included in the weekly NCE EPDs. Interims do not include genomics, but may be available on animals until genomic data is able to be incorporated into the weekly evaluation.
The most common answer to the question, "Why doesn't this animal have EPDs?", traces to the parents not having true NCE EPDs from the weekly evaluation. In many cases it is the dam that has interims. It is not possible to generate an interim EPD on an animal if one or both parents have interim EPDs without an individual weight record on the calf submitted in a proper contemporary group. More information about contemporary groups can be found here.
Once weights or genomic results are turned in on the calves, the parents and the calf will be added to the weekly evaluation, and the calf in question would have EPDs.
The individual weights on embryo transfer (ET) calves generally are not used in the weekly evaluation. However, if the ET calves are raised by registered Angus recipient cows, in a contemporary group of ET calves also raised by registered Angus recipients, we are able to incorporate the individual ET calf data into NCE. For calves born to non-registered Angus recipient cows, they can have interim EPDs until genomic or progeny data is added to the weekly evaluation.
ET calves out of commercial recipient dams receive only a pedigree-estimated interim EPD with a 0.05 accuracy, since the EPD is just the average of the sire EPD and the donor dam EPD. If the donor dam has interims, the ET calf will have no interim EPD.
Interim EPDs are temporary in a sense. We expect the typical animal to progress toward NCE EPDs, either by way of its own record or progeny data entering into the evaluations. The NCE EPDs take into account much more information than interims. Do not be shocked if the NCE EPD is not the same as the interim EPD.
Sometimes we invest too much confidence in an interim, as if we never expect change. EPDs change. Interim EPDs have low accuracies. Let's not forget that lower-accuracy animals are expected to have changes in their EPDs as more information becomes available on their genetic merit.
A calf with an interim EPD has a 0.05 accuracy associated with it. The animal's own performance is not included in the interim calculation. Utilize the possible-change tables available through the Association to help manage the interval of change expected on EPDs at a given accuracy level. Details on possible change associated with accuracy values are located here.
Also, don't be surprised to see bulls with a mixture of interim and NCE EPDs. It is a reflection of how much information was available to compute each EPD at the time the NCE was run.
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